本文详细介绍了Hibernate中一对多及多对多关系映射的方法，包括如何通过配置文件实现关联关系，解决性能问题，以及多对多关系下中间表的设计与使用。
/**
* 回顾：
* 表数据和表数据之间可以存在的关系？
* 建立关系的好处：对于多表查询关系数据的时候
* 一对多：
* 原则：在多的一方建立一个字段当成外键,指向一的一方的主键
* 多对多：
* 在外部创建一张中间表,让这个中间表中至少有2个字段分别指向各自表的主键
* 一对一：
* 让各自表的主键字段当成外键,指向另一张表的主键
* Hibernate是怎么做一对多的关系映射？
* 例如：客户与联系人
* 在一的一方有多的一方的集合
* 在多的一方有一的一方的对象
* (请看代码...)
* 当运行的测试,在保存一个客户和一个联系人的过程中,发现有2条insert语句,和一条update语句
* 虽然update语句不影响程序,但影响了性能
* 要想这些sql语句(update)能不能就不要出现了..
* 解决方案：
* 因为2方都维护了外键;让其中一方放弃不在维护外键即可
* inverse让外键失效
* <set name="linkmans" inverse="true" cascade="save-update">
* <key column="lkm_cust_id"></key>
* <one-to-many class="xinfei.code.domain.Linkman"/>
* </set>
*
* Hibernate是怎么做多对多的关系映射？
* @author zx
*
*/hibernate.cfg.xml配置
<?xml version="1.0" encoding="UTF-8"?>
<!-- 约束可以在hibernate-core-5.0.7.Final.jar->org.hibernate倒数dtd约束大概10行 -->
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- 配置数据库的信息 ps:去hibernate-release-5.0.7.Final\project\etc\hibernate.properties -->
<!-- 配置mysql驱动 -->
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<!-- 配置mysql数据库地址 -->
<property name="hibernate.connection.url">jdbc:mysql:///hibernate</property>
<!-- 配置mysql数据库的用户名 -->
<property name="hibernate.connection.username">root</property>
<!-- 配置mysql数据库的密码 -->
<property name="hibernate.connection.password">root</property>
<!-- 配置方言 告诉hibernate生成的sql数符合我当前数据库的sql语句 例子: 分页 mysql: select * from
表 limit ?,? sqlserver: select * from 表 top ?,? oracle: 自己手写sql嵌套 -->
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
<!-- 为hibernate配置c3p0 -->
<property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property>
<!-- 为了让hibernate生成的sql语句在控制台显示出来 -->
<property name="hibernate.show_sql">true</property>
<!-- 为了让显示的sql语句格式化好看点 -->
<property name="hibernate.format_sql">true</property>
<!-- 配置让hibernate根据映射关系给自动生成数据库的表 默认是不生成的 取值: create:没有表创建表,有表了删除表在创建 create-drop:没有表创建表,有表了删除表在创建
用完再删 update: 用它 没有表创建表 有表使用表 validate: 默认值 不让hibernate创建 -->
<property name="hibernate.hbm2ddl.auto">update</property>
<!-- 引入映射文件地址 -->
<mapping resource="xinfei/code/domain/Customer.hbm.xml" />
<mapping resource="xinfei/code/domain/Linkman.hbm.xml" />
<mapping resource="xinfei/code/domain/User.hbm.xml" />
<mapping resource="xinfei/code/domain/Role.hbm.xml" />
</session-factory>
</hibernate-configuration>package xinfei.code.domain;
import java.util.HashSet;
import java.util.Set;
/**
* 客户表 一对多的关系 一个客户可以对应多个联系人
*
* @author zx
*
*/
public class Customer {
public Long cust_id;// '客户编号(主键)',
public String cust_name;// '客户名称(公司名称)',
public String cust_source;// '客户信息来源',
public String cust_industry;// '客户所属行业',
public String cust_level;// '客户级别',
public String cust_phone;// '固定电话',
public String cust_mobile;// '移动电话',
private Set<Linkman> linkmans = new HashSet<Linkman>();
public Customer() {
super();
}
public Set<Linkman> getLinkmans() {
return linkmans;
}
public void setLinkmans(Set<Linkman> linkmans) {
this.linkmans = linkmans;
}
public Long getCust_id() {
return cust_id;
}
public void setCust_id(Long cust_id) {
this.cust_id = cust_id;
}
public String getCust_name() {
return cust_name;
}
public void setCust_name(String cust_name) {
this.cust_name = cust_name;
}
public String getCust_source() {
return cust_source;
}
public void setCust_source(String cust_source) {
this.cust_source = cust_source;
}
public String getCust_industry() {
return cust_industry;
}
public void setCust_industry(String cust_industry) {
this.cust_industry = cust_industry;
}
public String getCust_level() {
return cust_level;
}
public void setCust_level(String cust_level) {
this.cust_level = cust_level;
}
public String getCust_phone() {
return cust_phone;
}
public void setCust_phone(String cust_phone) {
this.cust_phone = cust_phone;
}
public String getCust_mobile() {
return cust_mobile;
}
public void setCust_mobile(String cust_mobile) {
this.cust_mobile = cust_mobile;
}
@Override
public String toString() {
return "Customer [cust_id=" + cust_id + ", cust_name=" + cust_name + ", cust_source=" + cust_source
+ ", cust_industry=" + cust_industry + ", cust_level=" + cust_level + ", cust_phone=" + cust_phone
+ ", cust_mobile=" + cust_mobile + "]";
}
}
package xinfei.code.domain;
/**
* 联系人表
*
* @author zx
*
*/
public class Linkman {
private Long lkm_id;// '联系人编号(主键)',
private String lkm_name;// '联系人姓名',
private String lkm_gender;// '联系人性别',
private String lkm_phone;// '联系人办公电话',
private String lkm_mobile;// '联系人手机',
private String lkm_email;// '联系人邮箱',
private String lkm_qq;// '联系人qq',
private String lkm_position;// '联系人职位',
private String lkm_memo;// '联系人备注',
private Customer customer;
public Linkman() {
super();
}
public Long getLkm_id() {
return lkm_id;
}
public void setLkm_id(Long lkm_id) {
this.lkm_id = lkm_id;
}
public String getLkm_name() {
return lkm_name;
}
public void setLkm_name(String lkm_name) {
this.lkm_name = lkm_name;
}
public String getLkm_gender() {
return lkm_gender;
}
public void setLkm_gender(String lkm_gender) {
this.lkm_gender = lkm_gender;
}
public String getLkm_phone() {
return lkm_phone;
}
public void setLkm_phone(String lkm_phone) {
this.lkm_phone = lkm_phone;
}
public String getLkm_mobile() {
return lkm_mobile;
}
public void setLkm_mobile(String lkm_mobile) {
this.lkm_mobile = lkm_mobile;
}
public String getLkm_email() {
return lkm_email;
}
public void setLkm_email(String lkm_email) {
this.lkm_email = lkm_email;
}
public String getLkm_qq() {
return lkm_qq;
}
public void setLkm_qq(String lkm_qq) {
this.lkm_qq = lkm_qq;
}
public String getLkm_position() {
return lkm_position;
}
public void setLkm_position(String lkm_position) {
this.lkm_position = lkm_position;
}
public String getLkm_memo() {
return lkm_memo;
}
public void setLkm_memo(String lkm_memo) {
this.lkm_memo = lkm_memo;
}
public Customer getCustomer() {
return customer;
}
public void setCustomer(Customer customer) {
this.customer = customer;
}
@Override
public String toString() {
return "Linkman [lkm_id=" + lkm_id + ", lkm_name=" + lkm_name + ", lkm_gender=" + lkm_gender + ", lkm_phone="
+ lkm_phone + ", lkm_mobile=" + lkm_mobile + ", lkm_email=" + lkm_email + ", lkm_qq=" + lkm_qq
+ ", lkm_position=" + lkm_position + ", lkm_memo=" + lkm_memo + ", customer=" + customer + "]";
}
}
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="xinfei.code.domain.Customer" table="cst_customer">
<id name="cust_id" column="cust_id">
<generator class="native"></generator>
</id>
<property name="cust_name" column="cust_name"></property>
<property name="cust_source" column="cust_source"></property>
<property name="cust_industry" column="cust_industry"></property>
<property name="cust_level" column="cust_level"></property>
<property name="cust_phone" column="cust_phone"></property>
<property name="cust_mobile" column="cust_mobile"></property>
<!-- 建立客户和联系人的一对多关系 name：是多的一方集合对象 inverse：让外键失效 cascade：级联配置 save-update：级联保存值
delete:级联删除值 即级联保存又级联删除：save-update,delete lazy: true:延迟加载(默认);false：立即加载 -->
<set lazy="false" name="linkmans" inverse="true" cascade="save-update,delete">
<!-- 外键的字段名 -->
<key column="lkm_cust_id"></key>
<!-- 对方的全限定名 -->
<one-to-many class="xinfei.code.domain.Linkman" />
</set>
</class>
</hibernate-mapping>
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="xinfei.code.domain.Linkman" table="cst_linkman">
<id name="lkm_id" column="lkm_id">
<generator class="native"></generator>
</id>
<property name="lkm_name" column="lkm_name"></property>
<property name="lkm_gender" column="lkm_gender"></property>
<property name="lkm_phone" column="lkm_phone"></property>
<property name="lkm_mobile" column="lkm_mobile"></property>
<property name="lkm_email" column="lkm_email"></property>
<property name="lkm_qq" column="lkm_qq"></property>
<property name="lkm_position" column="lkm_position"></property>
<property name="lkm_memo" column="lkm_memo"></property>
<!-- 建立客户和联系人的一对多关系 Customer customer many-to-one: 在多的一方做一对多关系建立的 name:
在自己里面一的一方对象属性名 class: 一的一方的全限定名 column:外键的字段名称 -->
<many-to-one cascade="save-update" name="customer"
class="xinfei.code.domain.Customer" column="lkm_cust_id"></many-to-one>
</class>
</hibernate-mapping>package xinfei.code.test;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;
import xinfei.code.domain.Customer;
import xinfei.code.domain.Linkman;
import xinfei.code.utils.HibernateUtils;
public class MoreToOneTest {
@Test
/**
* 创建一对多的表关系
*/
public void test01(){
Session openSession = HibernateUtils.openSession();
}
@Test
//保存第一个客户与联系人
public void test02(){
Session session = HibernateUtils.openSession();
//开启事务
Transaction transaction = session.beginTransaction();
Customer customer = new Customer();
customer.setCust_name("刘总");
Linkman linkman = new Linkman();
linkman.setLkm_name("联系人_01");
customer.getLinkmans().add(linkman);
linkman.setCustomer(customer);
session.save(customer);
session.save(linkman);
transaction.commit();
session.close();
}
/**
* 保存一个用户和多个联系人
*/
@Test
public void test03(){
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
//创建一个用户
Customer customer = new Customer();
customer.setCust_name("马总");
//创建多个联系人
Linkman linkman01 = new Linkman();
linkman01.setLkm_name("一对多-客服_01号");
Linkman linkman02 = new Linkman();
linkman02.setLkm_name("一对多-客服_02号");
Linkman linkman03 = new Linkman();
linkman03.setLkm_name("一对多-客服_03号");
Linkman linkman04 = new Linkman();
linkman04.setLkm_name("一对多-客服_04号");
//客户保存联系人
customer.getLinkmans().add(linkman01);
customer.getLinkmans().add(linkman02);
customer.getLinkmans().add(linkman03);
customer.getLinkmans().add(linkman04);
//联系人保存用户
linkman01.setCustomer(customer);
linkman02.setCustomer(customer);
linkman03.setCustomer(customer);
linkman04.setCustomer(customer);
//保存用户
session.save(customer);
//保存联系人
session.save(linkman01);
session.save(linkman02);
session.save(linkman03);
session.save(linkman04);
//提交
transaction.commit();
session.close();//关闭
}
/**
* 级联保存.保存客户的时候就把联系人保存了
*/
@Test
public void test04(){
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
//创建一个用户
Customer customer = new Customer();
customer.setCust_name("邓总");
//创建多个联系人
Linkman linkman01 = new Linkman();
linkman01.setLkm_name("一对多级联保存-客服_01号");
Linkman linkman02 = new Linkman();
linkman02.setLkm_name("一对多级联保存-客服_02号");
Linkman linkman03 = new Linkman();
linkman03.setLkm_name("一对多级联保存-客服_03号");
Linkman linkman04 = new Linkman();
linkman04.setLkm_name("一对多级联保存-客服_04号");
//客户保存联系人
customer.getLinkmans().add(linkman01);
customer.getLinkmans().add(linkman02);
customer.getLinkmans().add(linkman03);
customer.getLinkmans().add(linkman04);
//联系人保存用户
linkman01.setCustomer(customer);
linkman02.setCustomer(customer);
linkman03.setCustomer(customer);
linkman04.setCustomer(customer);
//保存用户
session.save(customer);
/**
* 当在保存用户的时候,hibernate配置
* cascade：
* 级联配置 save-update：级联保存值 delete:级联删除值 即级联保存又级联删除：save-update,delete
*/
//提交
transaction.commit();
session.close();//关闭
}
/**
* 测试删除数据
*/
@Test
public void test05(){
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
//创建一个用户
Customer customer = new Customer();
customer.setCust_name("级联删除");
//创建多个联系人
Linkman linkman01 = new Linkman();
linkman01.setLkm_name("测试删除数据-一对多级");
Linkman linkman02 = new Linkman();
linkman02.setLkm_name("测试删除数据-一对多级");
Linkman linkman03 = new Linkman();
linkman03.setLkm_name("测试删除数据-一对多级联");
Linkman linkman04 = new Linkman();
linkman04.setLkm_name("测试删除数据-一对多级联");
//客户保存联系人
customer.getLinkmans().add(linkman01);
customer.getLinkmans().add(linkman02);
customer.getLinkmans().add(linkman03);
customer.getLinkmans().add(linkman04);
//联系人保存用户
linkman01.setCustomer(customer);
linkman02.setCustomer(customer);
linkman03.setCustomer(customer);
linkman04.setCustomer(customer);
//保存用户
session.save(customer);
//提交
transaction.commit();
session.close();//关闭
}
/**
* 删除,把一个用户删除了
*/
@Test
public void delTest06(){
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
Customer customer = session.get(Customer.class,4L);
session.delete(customer);
transaction.commit();
session.close();
}
/**
* 删除,级联删除
*/
@Test
public void delTest07(){
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
/**
* 级联删除,需要hibernate配置
* cascade：
* 级联配置 save-update：级联保存值 delete:级联删除值
* 即级联保存又级联删除：save-update,delete
*/
Customer customer = session.get(Customer.class,4L);
session.delete(customer);
transaction.commit();
session.close();
}
}
package xinfei.code.domain;
import java.util.HashSet;
import java.util.Set;
public class Role {
private Long role_id;// 主键
private String role_name;// '角色名称',
private String role_memo;// '备注',
private Set<User> users = new HashSet<User>();//用户集合
public Role() {
super();
}
public Long getRole_id() {
return role_id;
}
public void setRole_id(Long role_id) {
this.role_id = role_id;
}
public String getRole_name() {
return role_name;
}
public void setRole_name(String role_name) {
this.role_name = role_name;
}
public String getRole_memo() {
return role_memo;
}
public void setRole_memo(String role_memo) {
this.role_memo = role_memo;
}
public Set<User> getUsers() {
return users;
}
public void setUsers(Set<User> users) {
this.users = users;
}
@Override
public String toString() {
return "Role [role_id=" + role_id + ", role_name=" + role_name + ", role_memo=" + role_memo + ", users=" + users
+ "]";
}
}
package xinfei.code.domain;
import java.util.HashSet;
import java.util.Set;
public class User {
private Long user_id;// '用户id',
private String user_code;// '用户账号',
private String user_name;// '用户名称',
private String user_password;// '用户密码',
private String user_state;// '1:正常,0:暂停',
private Set<Role> roles = new HashSet<Role>();// 角色集合
public User() {
super();
}
public Long getUser_id() {
return user_id;
}
public void setUser_id(Long user_id) {
this.user_id = user_id;
}
public String getUser_code() {
return user_code;
}
public void setUser_code(String user_code) {
this.user_code = user_code;
}
public String getUser_name() {
return user_name;
}
public void setUser_name(String user_name) {
this.user_name = user_name;
}
public String getUser_password() {
return user_password;
}
public void setUser_password(String user_password) {
this.user_password = user_password;
}
public String getUser_state() {
return user_state;
}
public void setUser_state(String user_state) {
this.user_state = user_state;
}
public Set<Role> getRoles() {
return roles;
}
public void setRoles(Set<Role> roles) {
this.roles = roles;
}
@Override
public String toString() {
return "User [user_id=" + user_id + ", user_code=" + user_code + ", user_name=" + user_name + ", user_password="
+ user_password + ", user_state=" + user_state + ", roles=" + roles + "]";
}
}
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="xinfei.code.domain.Role" table="sys_role">
<id name="role_id" column="role_id">
<generator class="native"></generator>
</id>
<property name="role_name" column="role_name"></property>
<property name="role_memo" column="role_memo"></property>
<set name="users" table="sys_user_role" inverse="true">
<key column="role_id"></key>
<many-to-many class="xinfei.code.domain.User" column="user_id"></many-to-many>
</set>
</class>
</hibernate-mapping><?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="xinfei.code.domain.User" table="sys_user">
<id name="user_id" column="user_id">
<generator class="native"></generator>
</id>
<property name="user_code" column="user_code"></property>
<property name="user_name" column="user_name"></property>
<property name="user_password" column="user_password"></property>
<property name="user_state" column="user_state"></property>
<!-- 建立多对多的关系 设置集合 private Set<Role> roles name:集合名称 table:要生成的中间表表名称 -->
<set name="roles" table="sys_user_role">
<!-- 自己在中间表的外键字段名 -->
<key column="user_id"></key>
<!-- class: 对方的全限定名 column: 对方在中间表的外键字段名称 -->
<many-to-many class="xinfei.code.domain.Role" column="role_id"></many-to-many>
</set>
</class>
</hibernate-mapping>package xinfei.code.test;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;
import xinfei.code.domain.Customer;
import xinfei.code.domain.Role;
import xinfei.code.domain.User;
import xinfei.code.utils.HibernateUtils;
public class MaryToMaryTest {
/**
* 多对多测试数据
* 需求：保存2个用户,3个角色
*/
@Test
public void test01(){
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
//创建两个用户
User user01 = new User();
user01.setUser_name("多对多-用户01");
User user02 = new User();
user02.setUser_name("多对多-用户02");
//创建3个角色
Role role01 = new Role();
role01.setRole_name("多对多-角色01");
Role role02 = new Role();
role02.setRole_name("多对多-角色02");
Role role03 = new Role();
role03.setRole_name("多对多-角色03");
//做用户与角色关联
user01.getRoles().add(role01);
user01.getRoles().add(role02);
user02.getRoles().add(role01);
user02.getRoles().add(role03);
//角色和用户关联
role01.getUsers().add(user01);
role01.getUsers().add(user02);
role02.getUsers().add(user01);
role03.getUsers().add(user02);
//保存用户
session.save(user01);
session.save(user02);
//保存角色
session.save(role01);
session.save(role02);
session.save(role03);
/**
* 当commit的时候,会报一个错,意思就是说其中一条已存在
* 原因:两张表都在维护,创建了相同的数据
* 解决：让一方放弃维护,（一般就是被动方放弃维护）
* 在Role.hbm.xml 配置 inverse="true"
* <set name="users" table="sys_user_role" inverse="true">
*/
transaction.commit();
session.close();
}
/**
* 对于多对多关心是中间表的分配
* 给用户的CRUD
* 给用户添加一个角色
*/
@Test
public void test02(){
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
//获取一个用户
User user = session.get(User.class,1L);
//获取一个角色
Role role = session.get(Role.class,7L);
//给这个用户添加获取这个角色
user.getRoles().add(role);
//持久态对象 只要修改了任意属性,会自动更新到数据库
transaction.commit();
session.close();
}
/**
* 删除一个角色
*/
@Test
public void test03(){
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
//获取一个用户
User user = session.get(User.class,1L);
Role role = session.get(Role.class,8L);
user.getRoles().remove(role);
transaction.commit();
session.close();
}
/**
* 修改一个用户角色
*/
@Test
public void test04(){
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
//获取一个用户
User user = session.get(User.class, 1L);
Role role = session.get(Role.class, 6L);
//
Role update_role = session.get(Role.class,7L);
user.getRoles().remove(role);
user.getRoles().add(update_role);
transaction.commit();
session.close();
}
/**
* 对象导航查询
* 意思就是做查询的时候,不只会查询对象本身的数据,当对象中还有别的对象或集合的时候,会把里面对象或集合的数据也一并给查询出来
*/
@Test
public void test05(){
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
Customer customer = session.get(Customer.class,1L);
System.out.println("customer信息：" + customer.getLinkmans());
transaction.commit();
session.close();
}
}
package xinfei.code.utils;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtils {
static Configuration configure = null;
static SessionFactory sessionFactory = null;
static{
configure = new Configuration().configure();
sessionFactory = configure.buildSessionFactory();
}
//获取session链接方法
public static Session openSession(){
return sessionFactory.openSession();
}
//从当前线程中获取session的方法
public static Session getCurrentSession(){
return sessionFactory.getCurrentSession();
}
}
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